Apparatus for monitoring the use of various associated devices are well known. Such monitoring apparatus may be used to both control the use of the associated device so that unauthorized personnel may not make use thereof and to record the number of times or the length of time the associated device is used. One application where such apparatus has found particular usefulness is in association with photocopy machines. Thus, it is often desirable to insure that only properly authorized personnel are permitted to use photocopy machines and that when a particular user does make use of a machine, the number of copies he makes is accurately recorded. Recording of the number of copies made has at least two beneficial effects. It allows the costs of operating a photocopy machine to be properly allocated among the users thereof and it often has the psychological benefit of inhibiting the making of needless copies.
However, the monitoring apparatus previously known have had a number of disadvantages associated therewith. Those available for use with photocopy machines have been particularly undesirable. For example, one common system makes use of electrically operated mechanical counters. In order for the user to operate a copying machine, he must insert a counter into a receptacle in a terminal associated with the copying machine. Each time a copy is made, the counter is advanced by one. The counters, of course, are relatively bulky and inconvenient to carry on one's person. Moreover, supplying each authorized user with his own counter is often prohibitively expensive, so that one counter must be made to do for an entire department. Every time it is desired to make an accounting of the copies made, all the counters must be physically examined and the results manually recorded. Another common system includes a plurality of counters as a part of a terminal associated with each photocopy machine. Each terminal has a lock associated therewith which must be operated by, for example, a key. In order to enable the copier to operate, one of the locks must be operated. Whenever a copy is made, the counter associated with the operated lock is advanced. This system has the disadvantage that only a relatively small number of counters can be accommodated in each terminal. When an accounting is to be made, each of the counters on each of the copiers must be examined and, again, the results manually recorded.
In the development of more sophisticated apparatus for monitoring the use of various devices and, in particular, photocopy machines, it is most important that the apparatus itself be relatively inexpensive and, additionally, that the information it provides be in an easily used form. Moreover, the monitoring apparatus should not necessarily detract from the ease with which the monitored device may be operated. Electrical counting and recording apparatus are, of course, desirable because of their extreme versatility. A great deal of information may be easily recorded and the information may be in a machine readable form able to be processed using conventional computer techniques. However, in order to reduce cost, it is desirable that a single recording device be capable of recording the use of a plurality of monitored devices. Moreover, it is desirable that the electrical interconnections between the single recording device and any apparatus associated with the individual monitored devices be kept as simple, and thus as economical, as possible. Further, it is important that the system be such that more than one of the monitored devices may be operated simultaneously without interfering with the monitoring functions.